Manufacturing method for semiconductor devices

ABSTRACT

The present invention is provided to prevent yield reduction of semiconductor device in dry cleaning of semiconductor device manufacturing process. The electric action and chemical action due to plasma of a first gas generated by means of a plasma generating means and the physical action due to viscous friction force of high speed gas flow generated by means of a planar pad that is brought close to the main surface of a wafer are applied together for cleaning the main surface of the wafer. After cleaning, the wafer is exposed to plasma of a second gas in the same vacuum chamber and then transferred to the atmosphere.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a manufacturing method for semiconductordevices involving cleaning, and particularly relates to a manufacturingmethod for semiconductor devices involving cleaning process to removeresidual particles on the semiconductor wafer surface.

2. Description of Related Art

A manufacturing method for semiconductor devices involving fineprocessing (LSI, VLSI and the like) has been developed. In thissituation, a cleaning process for cleaning semiconductor devices is oneof important processes in manufacturing process for improvingmanufacturing yield of semiconductor device. Cleaning is carried out aspre-treatment or aftertreatment of some processes such as film formingand etching.

Conventionally, semiconductor wafers (referred to as wafers hereinafter)are cleaned with pure water or diluted solution containing various acidsor alkalis in pure water by means of dipping of wafer in the solution orspraying of the solution on wafer to clean off particles on the wafersurface. A method in which a wafer is dipped in a solution and the wafersurface is brushed mechanically in the solution has also been employed.Such cleaning method is called “wet cleaning” because of the fact that asolution is used.

However, wet cleaning requires subsequent rinsing and drying processesin addition to cleaning process to result in increased multi-stepprocess. The multi-step process is a problem.

Dry cleaning has been known as cleaning method that solves the problemof wet cleaning.

One of the dry cleaning methods is disclosed in, for example, JP-A No.131981/1996 (referred to as known literature 1 hereinafter). Accordingto the known literature 1, an object to be cleaned, for example, a6-inch silicon wafer for semiconductor that has been formed by slicing,lapping, and polishing a single crystal silicone, is cleaned withactivated air at dry room temperature condition to remove particlesadsorbed electrostatically on the object to be cleaned. In detail, theactivated air contains air ions and water clusters to form high humidityatmosphere. The flowing activated air cleans an object to be cleaned ina cleaning chamber in contact with the object. The air ions neutralizeelectric charges of the object to be cleaned, and the water clustersisolate particles from the surface of the object to be cleaned. Theflowing activated air peels off and removes particles. The knownliterature 1 discloses pre-treatment cleaning for LSI manufacturing thatis carried out after purchase of Si wafer from a wafer maker in detail.

Another dry cleaning method is disclosed in JP-A No. 85887/1996(referred to as known literature 2 hereinafter) According to the knownliterature 2, a W sample to be etched having single film or laminatedfilm is etched, and then transferred to an aftertreatment equipment(treatment equipment used in the next process) by means of a vacuumtransfer equipment. Resist and particles are removed (plasma ashing)together in the aftertreatment equipment (in vacuum) without exposingthe sample in the atmosphere.

Yet another dry cleaning method is disclosed in JP-A No. 17776/1997(referred to as known literature 3 hereinafter). According to the knownliterature 3, to form a film that is accessible to adsorbed organicsubstance on a semiconductor substrate when the film is formed, the filmis cleaned with O₃ in room temperature or high temperature condition inthe same semiconductor manufacturing equipment to remove adsorbedorganic substance before film forming of an under layer film and tothereby stabilize film forming that is sensitive to the surfacecondition of the semiconductor substrate. In other words, according tothe known literature 3, O₃ gas is introduced into the semiconductormanufacturing equipment that was used to form the under layer wiringpattern on the semiconductor substrate to clean the semiconductorsubstrate. At that time, O₃ gas reacts with residual organic substanceon the semiconductor surface, and the organic substance is removed inthe form of volatile products such as CO or CO₂.

Recently, system-on-chip (so-called system LSI) that is typical of jobshop type product has become major instead of DRAM that is typical ofless-item mass-production type product. The job shop type productionregards short TAT (Turn Around Time) important to increase theproduction efficiency.

Hence it is required to employ dry cleaning process for cleaning that iscarried out as pre-treatment or aftertreatment of semiconductor devicemanufacturing process.

High performance device requires new materials including hygroscopicfilm materials such as organic film that is so-called as Low-k film (lowdielectric constant film having a dielectric constant of 3.0 or lower)and porous organic film such as interlayer dielectric. Wet cleaning andeven the exposure to the atmosphere cause conversion of device qualityin semiconductor device manufacturing process in which such newmaterials are used.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a cleaning methodfor cleaning semiconductor devices effectively in vacuum by means ofcleaning in vacuum in semiconductor device manufacturing process tosolve the problem of wet cleaning.

It is another object of the present invention to improve themanufacturing yield and reduce the cost in the semiconductor devicemanufacturing process.

It is another object of the present invention to improve the precisionand bring about low cost production of semiconductor devices in 0.1 μmprocess.

According to the present invention, cleaning is carried out efficientlyin dry and vacuum atmosphere. Particularly, the present invention isapplied effectively for cleaning of substrates (wafer) in semiconductordevice manufacturing process for manufacturing semiconductor devicescontaining material that is sensitive to moisture, excessive chemicals,and excessive force.

There are many contact holes (through holes) and corners of wiring onthe main surface of a wafer in semiconductor device manufacturingprocess. The cleaning effect on such wafer surface will be describedherein under briefly.

The viscous friction due to gas flow acts physically to remove particles59 that are deposited in the space between the main surface of a padshape substance and the surface of a wafer, and hence the cleaning iseffective over the area on which the gas is flowing.

On the other hand, in the conventional wet cleaning, it is difficult forthe liquid to penetrate into fine space because of the surface tensionof the liquid, the cleaning effect is insufficient for the processinvolving dimension of 0.3 μm or smaller. However, because gas flow isused in the present invention, the cleaning is effective forsemiconductor integrated circuit devices, which will have further finerstructure in the future.

According to the present invention, it is possible to improve theprocess efficiency and reduce the damage due to plasma by applyingplasma irradiation and frictional force simultaneously or separately inthe time.

Further more, according to the present invention, the conversion of awafer that is caused after exposure to the atmosphere is prevented bytreating with plasma of the second gases after the wafer is cleaned, andhence the high precision and high yield semiconductor devicemanufacturing process is performed.

Further particularly, the manufacturing method for semiconductor devicesof the present invention is effective for manufacturing of system LSI,which requires short TAT, such as LSI having memo LSI and logic LSImixedly. The efficient cleaning brings about short time, low cost, andhigh yield manufacturing of system LSI.

An invention that is representative in the inventions disclosed in thepresent invention will be described briefly herein under.

One of the inventions involves a manufacturing method for semiconductordevices including:

a step for preparing a dry cleaning system having a vessel connected toa vacuum pump, a means for generating plasma, a gas supply means forsupplying gas that is material for generating plasma, a wafer stageprovided in the vessel on which the wafer is set, a planar pad providedwith a gas hole for injecting gas and a flat part facing to the wafer,and a means for scanning the planar pad on the wafer surface;

a step for setting the wafer on the wafer stage;

a step in which the vessel is maintained vacuum by means of the vacuumpump, gas that is material for generating plasma is supplied into thevessel by means of the gas supply means, and plasma is generated in thevessel by means of the means for generating plasma;

a step in which the flat part of the planar pad is brought close to thewafer main surface and the first gas is injected from the gas hole tothereby apply the flow frictional force due to gas flow of the first gasand action of electric charges or radicals generated by means of plasmasimultaneously, and the main surface of the wafer is cleaned;

a step in which plasma of a second gas is generated in the vessel andthe main surface of the wafer is exposed to the plasma after theabove-mentioned cleaning step; and

a step for transferring the wafer to the outside of the vessel.

The above-mentioned and other objects and innovative characteristics ofthe present invention will be apparent from the detailed description andattached drawings of the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail based on the followings, wherein:

FIG. 1 is a basic structural diagram of a dry cleaning system to beapplied to the present invention;

FIG. 2A is a structural side view of a planar pad of the dry cleaningsystem to be applied to the present invention;

FIG. 2B is a structural plan view of a dry cleaning system to be appliedto the present invention;

FIG. 3 is a cleaning flow chart applied in embodiment 1 of the presentinvention;

FIG. 4 is a cleaning flow chart applied in embodiment 2 of the presentinvention;

FIG. 5A is a process diagram showing a step of the manufacturing processfor a semiconductor device in embodiment 3 of the present invention;

FIG. 5B is a process diagram showing a step of the manufacturing processfor a semiconductor device in embodiment 3 of the present invention;

FIG. 5C is a process diagram showing a step of the manufacturing processfor a semiconductor device in embodiment 3 of the present invention;

FIG. 5D is a process diagram showing a step of the manufacturing processfor a semiconductor device in embodiment 3 of the present invention;

FIG. 5E is a process diagram showing a step of the manufacturing processfor a semiconductor device in embodiment 3 of the present invention;

FIG. 5F is a process diagram showing a step of the manufacturing processfor a semiconductor device in embodiment 3 of the present invention;

FIG. 6 is a cross sectional view of showing the manufacturing processfor a semiconductor device in embodiment 4 of the present invention;

FIG. 7 is an explanatory diagram showing particle removal in a contacthole (or through hole) in the present invention; and

FIG. 8 is an explanatory diagram showing particle removal on a wiringcorner in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

Structure of a dry cleaning system to be applied to the cleaning methodof the present invention will be described below with reference to FIG.1.

The word “wafer” described in the following detailed embodimentsgenerally includes silicon wafer, epitaxial wafer, compoundsemiconductor wafer (for example, GaAs wafer), and SOI wafer comprisinga semiconductor layer formed on a dielectric-layer unless otherwisespecified.

The structure of a dry cleaning system shown in FIG. 1 comprisesbasically a vessel (chamber) 1, a vacuum pump for reducing the pressurein the vessel 1 to a predetermined pressure, for example, a turbomolecular pump TMP having a capacity of 2000 1/sec, a means 2 forgenerating plasma, a means (mass flow controller MFC) 6 for supplyinggas that is to be raw material of plasma, a wafer setting means(circular stage) 3 on which a wafer is set that is a sample to beprocessed, a planar pad 5 having a function to inject gas against thewafer surface, and a swing motion mechanism 8 for scanning the planarpad 5 on the wafer surface.

The wafer 4 is transferred from a transfer chamber 12 connected througha valve 11 to the vessel 1 by means of a transfer arm 10, and set on thewafer setting means (wafer stage) 3.

CF₄, O₂, Ar, or Ar+H₂(3%), which is raw material of plasma, is suppliedfrom the gas supply means 6 to the vessel 1. A gas introduction means 7connected to the planar pad 5 having a function to inject gas isprovided independently of the gas supply means 6 for supplying gas thatis used as raw material of plasma to be generated by the plasmagenerating means.

Ar is injected from the gas supply means 6 against the main surface ofwafer 4 set on the circular stage 3 through the planar pad 5. The planarpad 5 is provided with the swing motion mechanism 8 for scanning on thewafer 4 surface and an actuator function 9 served to bring the planarpad 5 close to the wafer 4 surface. An infrared lamp 14 is provided nearthe vacuum vessel 1 so that infrared ray comes into the vessel 1 througha window 13. The light emitted from the infrared lamp 14 is irradiatedto heat the wafer though it is described hereinafter.

FIG. 2A and FIG. 2B show a detailed structural diagram of the planar pad5. FIG. 2A is a cross sectional view of the planar pad 5 and FIG. 2B isa plan view of a pad part 15. The planar pad 5 comprises a pad part 15that comes close to the wafer 4 surface, a pad holding part 16 forholding the pad part, a gas injecting part 17, a movable part 18 forbringing the pad part close to the surface to be processed always, and aload detection part 19 for detecting a load loaded between the wafersurface and the pad part when the pad part is brought close to the wafersurface. The load detection part 19 is connected electrically to acontrol part 20 shown in FIG. 1. The actuator function 9 is controlledthrough the control part 20 in response to the load detected by means ofthe load detection part 19 to thereby control the space between theplanar pad 5 and the wafer 4. The pad part 15 is formed of Teflon, whichis a material stage to plasma exposure. One of other materials such aspoly-vinyl alcohol, Derlin, Vespel, Kapton, poly-vinyl chloride,polyester, silicon oxide, silicon, and aluminum oxide may be used.

Next, a manufacturing process for semiconductor devices that employs theabove-mentioned dry cleaning system will be described with reference toFIG. 3.

(a) At first, a wafer 4 to be cleaned is transferred onto the wafersetting means 3 from the transfer chamber 12 by use of a transfer arm10. The wafer 4, for example, has a dielectric film (oxide film) on themain surface and a contact hole or through hole formed on the dielectricfilm.

(b) Subsequently, the internal of the vessel 1 is kept vacuum by meansof turbo molecular pump, and the wafer 4 is rotated in the circumferencedirection by means of rotation function of the wafer setting means 3. Inthe present embodiment 1, the wafer 4 is rotated at a rotational speedof 200 rpm. The rotation speed relates to the particle removalthroughput and is controlled optionally.

(c) Subsequently, CF₄ and O₂ are introduced into the vacuum vessel asthe first gas by means of the gas introducing means 6. At that time, 20sccm of CF₄ and 40 sccm of O₂ are introduced in the present embodiment 1as the first gas. The first gas is used as the raw material to generateplasma by means of the plasma generating means 2. Fluorine radials andminute electric charges supplied from the plasma onto the wafer 4surface reduce the adsorption force of fine particles adsorbed on thewafer 4 surface. For example, minute electric charge neutralizeselectric charges of fine particles adsorbed electrostatically on thewafer surface to thereby reduce the adsorption force. On the other hand,fluorine radical reduces the adsorption force of adsorption particles ofstick on surface by means of slight etching action on the wafer surface,and acts to reduce the chemical adsorption force itself betweenparticles and wafer surface.

(d) Subsequently, the pad part 15 of the planar pad 5 is brought closeto the wafer 4 surface to a distance of 100 μm or shorter by means ofthe actuator function 9 with injecting 15000 sccm of Ar gas from the gasinjecting part 17 of the planar pad 5. At that time, a repulsion forceacts between the planar pad 5 and the wafer 4 surface continuously whilethe planar pad 5 is coming close before contact because the planar pad 5comes close to the wafer 4 surface with injecting Ar gas. The loaddetection part 9 detects the repulsion force, and the control part 20controls the actuator function 9 so as to keep the load constant tothereby keep the distance between the planar pad 5 and the wafer 4surface constant.

In the present embodiment 1, the load is kept at 150 Newton to keep thedistance of 30 μm between the planar pad 5 and the wafer 4 surface. Inother words, the distance between the pad surface (15) and the wafersurface (4) is controlled by detecting the force that acts between thepad part 15 and wafer 4 by means of the load detection part 19. Indetail, Ar gas supplied from the planar pad 5 causes high gas pressurecondition in the space between the pad surface (15) and wafer surface(4). The load is caused between the pad part 15 and wafer 4 though thepad part is not in contact with the wafer 4, and hence the space betweenthe pad part and wafer surface is controlled by controlling the load andgas flow rate. A piezo device, strain meter, spring, elastic material,or weight may be used as the weight detection part 19, and a membercomprising combined these components may be used also as the weightdetection part 19. It is effective to keep the space of 1 to 100 μmbetween the pad part surface and the main surface of the wafer 4, andmore preferably space of 5 to 30 μm. The narrowest space between the padsurface and wafer surface gives the highest cleaning effect only inconsideration of cleaning effect, but the narrowest space does not allowthe space to be kept constant, and is apt to cause damage on the wafer 4surface due to possible contact when the space is narrowed excessively.Based on the above-mentioned reason, the space of 5 to 30 μm is mosteffective.

As described hereinabove, the proximity of the planar pad 5 to the wafersurface with injection of Ar gas generates high-speed gas flow betweenthe planar pad 5 and wafer 4. The gas flow causes viscous friction forcein the horizontal direction of the wafer surface. The viscous frictionforce causes substance movement force in non-contact condition. As theresult, fine particles adsorbed on the wafer 4 surface can be removed.According to the one of important points of the present invention, thefriction force due to the gas flow is utilized to remove particles 26adsorbed on the wafer surface.

(e) Furthermore, the planar pad 5 is swung on the wafer 4 surface. Theswing motion mechanism 8 of the planar pad 5 and the rotation functionof the wafer setting means 3 exert the viscous friction force due tohigh speed gas flow on the wafer 4 surface for a certain time (T1). Theviscous friction force is exerted on the entire wafer surface.

(f) Subsequently, the plasma of the first gas is stopped. In otherwords, the plasma generation is stopped.

(g) Subsequently, the planar pad 5 is moved aside from the wafer 4surface, and gas injecting from the gas injecting part 17 of the planarpad 5 is stopped. The cleaning is finished though the above-mentionedprocesses.

As described hereinabove, it is possible to remove particles on thewafer surface by applying adsorption force reduction of the particlesadsorbed on the wafer surface due to electric charges and radicalssupplied from plasma generated from the first gas and by applyingviscous friction force due to high speed gas flow generated between theplanar pad 5 and the wafer 4 surface that are brought close each other.

The control part 20 controls not only the actuator function 9 withsignal of the load transfer part 19 but also rotation of the wafersetting means 3, the gas introducing means 6, the gas introducing means7, the swing motion mechanism 8, the plasma generating means 2, and theinfrared lamp control part. These components function conformably to aprogram.

Considerable amount of fluorine remains on the wafer surface aftercleaning because plasma containing CF₄ gas is irradiated on the wafer inthe cleaning process. If the wafer that adsorbs fluorine is exposed tothe atmosphere, the fluorine reacts with moisture in the atmosphere togenerate hydrofluoric acid to thereby convert the wafer surfacepossibly. To avoid such trouble, it is required for the wafer to beexposed to the atmosphere after the fluorine, which is adsorbed on thewafer 4 surface after cleaning, is made harmless.

(h) After cleaning, the planar pad 5 is moved aside from the wafer 4surface. Then, hydrogen gas that is diluted with Ar to 3% (Ar+H₂(3%))and oxygen are introduced from the gas introducing means 6 as the secondgas, and plasma generated by means of the plasma generating means 2 isirradiated on the wafer 4 for a certain time (T2). H radicals of plasmagenerated from hydrogen raw material are supplied to the wafer surfaceto thereby convert the fluorine adsorbed on the wafer surface to HF. Theconverted HF is evaporated from the wafer surface because of vacuum andexhausted to the outside. As the result, fluorine is removed from thewafer 4 surface after cleaning, and conversion that would occur when thewafer 4 is exposed to the atmosphere is prevented.

The oxygen contained in the second gas is served to remove depositedfilm of reaction product of carbon and hydrogen that are residual in thevacuum vessel 1. The reason why hydrogen diluted with Ar gas is used isthat hydrogen diluted to the concentration of 3% or lower is notinflammable. The inflammability brings about safety and reduced cost forhandling. Dilution to a concentration of about 3% is sufficient.

The infrared lamp 14 heats the wafer 4 to a temperature of about 200degrees or lower during treatment of the wafer surface with plasma ofthe second gas after cleaning. The heating promotes HF on the wafer 4surface generated by H radicals to be evaporated to thereby result ineffective removal of HF.

Continuous heating of wafer by means of the infrared lamp 14 throughintroduction of the first gas for cleaning and introduction of thesecond gas brings about the same effective result. Overheating of thewafer 4 in cleaning also results in improved cleaning effect. The wafersurface is subjected to plasma and lamp heating uniformly throughout theentire wafer surface by rotating the wafer in this process.

(i) After the above-mentioned (h) process is completed, rotation of thewafer 4 is stopped.

(j) Subsequently, the valve 11 is opened, and the wafer 4 is transferredfrom the vessel 1 to the transfer chamber 12 by means of the transferarm 10.

Embodiment 2

Embodiment 2, which is different from embodiment 1, will be describedwith reference to FIG. 4. In embodiment 1, plasma generation from thefirst gas is carried out simultaneously with viscous friction forceapplication due to high-speed gas on the wafer 4 surface by means of theplanar pad. On the other hand, in embodiment 2, plasma generation fromthe first gas is carried out separately from viscous friction forceapplication due to high-speed gas on the wafer 4 surface by means of theplanar pad.

(a) A wafer 4 is set on the wafer setting means 3 in the dry cleaningsystem shown in FIG. 1.

(b) Subsequently, the wafer 4 is rotated by means of rotation functionof the wafer setting means 3. At that time, the planar pad 5 is apartfrom the wafer 4 surface.

(c) Subsequently, the first gas is converted to plasma by means of theplasma generating means and the plasma is irradiated on the rotatingwafer 4 for a certain time (T1) to thereby reduce the adsorption forceof particles adsorbed on the wafer 4 surface. This process is referredto as pre-treatment of cleaning that will be carried out in process (e).

(d) Subsequently, plasma generation is stopped.

(e) Subsequently, the planar pad 5 is replaced on the wafer 4 surfaceand brought close to the wafer 4 surface with injection of Ar gas in thesame manner as carried out in embodiment 1. Viscous friction force dueto high-speed gas flow is exerted on the entire surface of the wafer 4with horizontal swinging of the planar pad 5 on the wafer 4 surface.Cleaning by means of viscous friction force is carried out for a certaintime (T2) in this process.

(f) After process (e), the planar pad 5 is moved away from the wafer 4surface again. Injection of the gas from the planar pad 5 is stopped.

The above-mentioned cleaning process involving the plasma irradiation ofthe first gas and the viscous friction force is repeated as required toclean the wafer 4. In other words, the processing including from process(c) to process (f) is repeated as required. After completion ofcleaning, the sequence proceeds in the same manner as carried out inembodiment 1 as described herein under.

(g) After completion of cleaning, the planar pad 5 is moved away fromthe wafer 4 surface.

(h) Subsequently, hydrogen gas that is diluted with Ar to 3% (Ar+H₂(3%))and oxygen are introduced from the gas introducing means 6 as the secondgas, and plasma generated by means, of the plasma generating means 2 isirradiated on the wafer 4 for a certain time (T2). H radicals of plasmagenerated from hydrogen raw material are supplied to the wafer surfaceto thereby convert the fluorine adsorbed on the wafer surface to HF. Theconverted HF is evaporated from the wafer surface because of vacuum andexhausted to the outside.

As the result, fluorine is removed from the wafer 4 surface aftercleaning, and conversion that would occur when the wafer 4 is exposed tothe atmosphere is prevented. The oxygen contained in the second gas isserved to remove deposited film of reaction product of carbon andhydrogen that are residual in the vacuum vessel 1. The reason whyhydrogen diluted with Ar gas is used is that hydrogen diluted to theconcentration of 3% or lower is not inflammable. The inflammabilitybrings about safety and reduced cost for handling. Dilution to aconcentration of about 3% is sufficient.

The infrared lamp 14 heats the wafer 4 to a temperature of about 200degrees or lower during treatment of the wafer surface with plasma ofthe second gas after cleaning. The heating promotes HF on the wafer 4surface generated by H radicals to be evaporated to thereby result ineffective removal of HF. Continuous heating of wafer by means of theinfrared lamp 14 through introduction of the first gas for cleaning andintroduction of the second gas brings about the same effective result.Overheating of the wafer 4 in cleaning also results in improved cleaningeffect.

The wafer surface is subjected to plasma and lamp heating uniformlythroughout the entire wafer surface by rotating the wafer in thisprocess.

(i) After the above-mentioned (h) process is completed, rotation of thewafer 4 is stopped.

(j) Subsequently, the valve 11 is opened, and the wafer 4 is transferredfrom the vessel 1 to the transfer chamber 12 by means of the transferarm 10.

According to embodiment 2, plasma is not irradiated while the planar pad5 is being on the wafer 4 surface, and embodiment 2 is advantageous overthe above-mentioned embodiment 1 in the points described herein under.

In the process (c), the planar pad 5 is placed apart form the wafer 4surface. Therefore, the planar pad 5 will not prevent the irradiation ofplasma partially on the wafer 4 surface, and the entire surface of thewafer 4 is exposed to irradiation. The particle adsorption forcereduction effect is improved by action of plasma. Furthermore, theparticle adsorption force reduction effect distributes uniformly overthe entire surface of the wafer 4.

Furthermore, the wafer 4 surface that is not covered partially with theplanar pad 5 during plasma irradiation does not cause uneven potentialdue to plasma on the wafer 4 surface. As the result, devices such astransistors that are built in the wafer 4 surface are not subjected todamage.

The infrared lamp is used as a means for heating the wafer 4 in theembodiment 1 and embodiment 2, but a heater that is built in the wafersetting means 3 may be used to heat the wafer 4. Heating by the heatergives the same effect of the infrared lamp. The wafer setting means 3provided with a built-in heater is more effective for uniform heating ofthe entire surface of the wafer 4.

Furthermore, plasma generated from the second gas is used to removeradicals after cleaning in the embodiment 1 and embodiment 2, butheating of the wafer 4 at a temperature of, for example, 200 degrees to300 degrees by use of a heating means such as infrared lamp 14 in thevacuum vessel 1 may be employed to obtain the HF removal effect. Inother wards, the energy larger than the adsorption energy of fluorine isapplied to activate fluorine on the substrate surface to thereby causethermal dissociation and exhaustion of the fluorine.

A mixed gas containing CF₄ and oxygen (O₂), that is used for suppressingof deposition film formation) is used as the first gas in embodiment 1and embodiment 2. However, a mixed gas containing oxygen (O₂) and one ofgases selected from a group of a gas containing chlorine element such asCl₂ or BCl₃, a gas containing fluorine element such as C₂F₆, SF₆, F₂, orHF, and a gas containing hydrogen such as NH₃, H₂, or CH₄ may be used asother first gas. The type of the first gas is selected depending onmaterial and structure of the wafer surface to be cleaned. Therefore,oxygen (O₂) gas is used alone as the first gas depending on the case.

Ar is used as a gas that is injected from the planar pad 5 in embodiment1 and embodiment 2, but N₂, He, Ne, Kr, or Xe may be used to obtain thesame effect. Among these gases, Ar, He, and Ne are used advantageouslyin virtue of low cost and less chemical attack.

Furthermore, hydrogen diluted with Ar (Ar+H₂(3%)) and O₂ are used as thesecond gas in embodiment 1 and embodiment 2, but one of gases selectedfrom a group of Ne, Kr, Xe, He, and N₂ may be selected to obtain thesame effect.

Furthermore, plasma generated from any one of Ne, Kr, Xe, He, N₂, and O₂containing no hydrogen is sufficiently effective depending on the degreeof remaining radicals. Less residual radicals and less damage due to thefirst gas allows plasma processing with the second gas to be omitted,and only the overheating of wafer by means of the infrared lampdescribed in the above-mentioned embodiments may be applied to obtainsufficient effect.

In the case as described hereinabove, introduction of the second gas andplasma processing with the gas are not necessarily applied.

Embodiment 3

Next, an embodiment in which the cleaning method described in embodiment1 and embodiment 2 is applied in a step for forming active area in awafer will be described. Application of embodiment 1 or embodiment 2 inactive area forming stage is effective to prevent quality deteriorationof semiconductor devices such as MISFET.

A MISFET is formed according to the sequential processes shown in FIG.5A to FIG. 5F including (a) separation and forming of elements anddeposition of a gate polycrystalline silicon, (b) forming of a gateelectrode (etching of polycrystalline silicon), (c) forming of extension(N-area) by means of ion-implantation, (d) deposition of a nitride film,(e) forming of a gate electrode side wall protection film (etching ofnitride film), and (f) forming of silicide film. Cleaning described in,for example, embodiment 2 is carried out in the time between eachprocess and the next process. Processes (a) to (f) will be describedbriefly herein under.

(a) A groove separation area 46 is formed on a silicon substrate 45 toseparate element. The silicon substrate 45 comprises a p-type substrateon which a p-well is formed. Subsequently, a gate polycrystallinesilicon 47 is deposited with interposition of a gate oxide film (notshown in the drawing). The gate polycrystalline silicon 47 is formed byCVD in a vacuum processing chamber.

(b) The polycrystaliine silicon is dry-etched in the vacuum processingchamber to form a gate electrode 49.

(c) Extensions (N-areas 50 and 51) matching with the gate electrode 49are formed by ion implantation. The extension is a source-drain areahaving a relatively low concentration formed to cope with hot electrons.

(d) A nitride film 52 is deposited on the semiconductor substrate 45having the gate electrode 49 by plasma CVD.

(e) The nitride film 52 is subjected to dry-etching (anisotropicetching) to form a gate side wall protection film 53 on the side wall ofthe gate electrode 49. Dry cleaning described in embodiment 1 is carriedout thereafter. A contact N+ area (source and drain areas 50S and 51D)having a relatively high concentration matching with the gate side wallprotection film 53 is formed by ion implantation.

(f) Subsequently, silicide layers 54 are formed on the surface of thesource-drain areas 50S and 51 and the surface of the gate electrode 49to render it low-resistant. The silicide layer 4 is formed by, forexample, adsorbing cobalt on the source-drain areas 50S and 51D and thesurface of the gate electrode 49 and by heat-treating it.

CF₄+O₂ is used as the first gas in embodiment 3 as in the case ofembodiment 1 or embodiment 2. Hydrogen diluted with Ar is used as thesecond gas as in the case of embodiment 1 or embodiment 2.

Usually, wet cleaning with various chemical solutions is employed ingate electrode forming process of MISFET. Particles that remain aftereach process can be removed by dry cleaning according to the presentinvention, hence cleaning with chemical solution can be omitted orreduced significantly. Particularly, diluted chemical solution is enoughfor effective cleaning, and the dimension shift of the gate electrodeand waste solution treatment cost that are caused from chemical solutiontreatment is suppressed.

According to embodiment 3 described hereinabove, dry cleaning isemployed in the MISFET forming process between each process and the nextprocess to thereby result in improved manufacturing yield and reducedcost of high performance semiconductor devices. In the presentembodiment, the manufacturing process for semiconductor devices isdescribed with reference to the example of one MISFET shown in FIG. 11.A plurality of MISFETs that are described hereinabove are formedactually on one semiconductor substrate so as to constitute asemiconductor integrated circuit device such as LSI or VLSI.

Embodiment 4

FIG. 6 is a perspective view partially showing the manufacturing processfor semiconductor integrated circuit device. Particularly, a via contactforming process on an interlayer dielectric by dry etching is shown. Adielectric film 33 comprises a dielectric film consisting of lowdielectric constant material (organic-base material), which is called asLow-k and is effective for high speed operation and energy saving of thesemiconductor devices.

As shown in FIG. 6, the low dielectric film 33 is etched with plasmagenerated from a gas mainly containing hydrogen or ammonia to form a viacontact and groove to obtain dual damascene. In other words, a wafer(substrate 37) having a dielectric film on which a via contact andgroove are formed on the main surface is formed. A nitride film 34interposed between low dielectric constant films 33 is served as anetching stopper film that is effective when the upper low dielectricconstant film 33 is dry-etched.

Subsequently, dry cleaning is carried out. In the dry cleaning accordingto the present embodiment 4, the above-mentioned embodiment 1 isemployed. Hydrogen or ammonia is used as the first gas. Various porousmaterials, SiOC, or SiOF may be used in addition to organic-basematerial for the low dielectric constant film. The first gas and thesecond gas to be used in cleaning process of the present inventionare-selected suitably for the employed material. Usually, wet etching iscarried out with various chemical solutions after etching of theinterlayer dielectric. However, the dielectric film formed of lowdielectric constant material is generally weak to moisture andchemicals, and moisture and such chemicals causes conversion and filmperformance deterioration of the dielectric film.

Application of cleaning according to the present invention after etchingbrings about reduced wet cleaning and brings about improvedmanufacturing precision and yield of semiconductor devices having lowdielectric constant film.

Subsequently, Cu conduction layers are formed on the via contact 35 andgroove 36. Such conduction layer (wiring structure) comprises fourlayers or five layers though not shown in the drawing. Hence the finalyield depends significantly on the amount of residual particles afteretching of each layer. It is possible to improve the yield by applyingthe cleaning according to the present invention after etching of eachlayer.

The above-mentioned embodiment 2 may be employed for the dry cleaning inthe present embodiment 4.

In the above, the invention accomplished by the inventors of the presentinvention is described in detail based on the embodiments of theinvention, however, the present invention is by no means limited to theabove-mentioned embodiments, and various changes and modifications maybe made in the invention without departing from the sprit and scopethereof. Detailed examples are described herein under.

In some manufacturing process for semiconductor integrated circuitdevices, various conduction films (tungsten, aluminum, cobalt, or thelike) or dielectric films (SiO₂ or the like) are formed by spattering.It is effective to apply the dry cleaning according to the presentinvention after spattering. Careful cleaning is required after formingof a spattering film because spattering accompanies generation of muchdust generally. If wet brush cleaning is applied in this case, the waferis damaged mechanically depending on the device structure formed on thewafer surface because relatively strong force is exerted on the wafer.On the other hand, application of dry cleaning according to the presentinvention after forming of spattering film allows the wafer to becleaned without strong wet cleaning, and the freedom of the devicestructure is secured and the device manufacturing yield is improved.

In the above-mentioned embodiment 3, the wafer is subjected to thethrough process in vacuum without exposing to the atmosphere betweenetching process and dry cleaning process to thereby improve thereliability and productivity of the semiconductor integrated circuitdevices.

1. A manufacturing method for semiconductor devices by use of a drycleaning system having a vessel connected to a vacuum pump, a means forgenerating plasma, a gas supply means for supplying gas that is used forgenerating plasma, a wafer stage on which a wafer is to be set providedin said vessel, a planar pad provided with a gas hole for injecting gastoward the wafer and a flat part facing to the wafer, and a means forscanning said planar pad on said wafer, said manufacturing methodcomprises: a step for setting a wafer on said wafer stage, a step inwhich a flat gas that is used for generating plasma is supplied intosaid vessel by means of said gas supply means maintaining the internalof said vessel at a reduced pressure by use of said vacuum pump tothereby generate a first plasma in said vessel by means of said meansfor generating plasma; a step for cleaning the main surface of saidwafer by applying the viscous friction force exerted due to gas flow ofa third gas injected from said gas hole onto the main surface of saidwafer that is brought close to the flat part of said planar pad and byapplying action of electrons or radicals generated by said plasmatogether; a step in which a second plasma is generated using a secondgas in said vessel after said cleaning step and the main surface of saidwafer is exposed to said second plasma, said step including removing anelement of said first gas adsorbed on the wafer surface or a film of areaction product of said first gas deposited on the wafer surface; and astep for transferring said wafer to the outside of said vessel.
 2. Themanufacturing method for semiconductor devices according to claim 1,wherein a step for cleaning the main surface of said wafer with actionof electric charges or radicals generated from said first plasma isadded as a pre-treatment after the step in which said first plasma isgenerated in said vessel.
 3. The manufacturing method for semiconductordevices according to claim 2, wherein the third gas injected from saidplanar pad onto the wafer surface is any one gas of argon, helium, neon,krypton, xenon, and nitrogen.
 4. The manufacturing method forsemiconductor devices according to claim 1, wherein the component ofsaid first gas contains molecule containing any one element of chlorine,fluorine, hydrogen, and oxygen.
 5. The manufacturing method forsemiconductor devices according to claim 4, wherein said first gasincludes at least one of a gas containing chlorine is selected from agroup consisting of Cl₂ and BCl₃, a gas containing fluorine is selectedfrom a group consisting of CF₄, C₂F₆, SF₆, F₂, and HF, a gas containinghydrogen is selected from a group consisting of NH₃, H₂, and CH₄, and agas containing oxygen is selected from O₂.
 6. The manufacturing methodfor semiconductor devices according to claim 1, wherein oxygen gas isadded to the first gas.
 7. The manufacturing method for semiconductordevices according to claim 1, wherein a component of said second gascontains molecule containing hydrogen, and is diluted with any one gasof argon, neon, krypton, xenon, helium, and nitrogen.
 8. Themanufacturing method for semiconductor devices according to claim 1,wherein the second gas is any one gas of argon, neon, krypton, xenon,helium, nitrogen, and oxygen.
 9. The manufacturing method forsemiconductor devices according to claim 8, wherein oxygen is added tothe second gas.
 10. The manufacturing method for semiconductor devicesaccording to claim 1, wherein a gate electrode formed by means of dryetching is provided on the main surface of said wafer set on said waferstage.
 11. The manufacturing method for semiconductor devices accordingto claim 1, wherein a dielectric film is provided on the main surface ofsaid wafer set on said wafer stage, and a contact hole or through holeis provided on said dielectric film formed by means of dry etching. 12.The manufacturing method for semiconductor devices according to claim11, further comprising a step for burying a conductor layer in saidcontact hole or through hole after the step of generating said secondplasma.
 13. The manufacturing method for semiconductor devices accordingto claim 11, wherein said dielectric film comprises an organicdielectric film.
 14. A manufacturing method for semiconductor devices byuse of a dry cleaning system having a vessel connected to a vacuum pump,a means for generating plasma, a gas supply means for supplying gas thatis used for generating plasma, a wafer stage on which a wafer is to beset provided in said vessel, a planar pad provided with a gas hole forinjecting gas toward the wafer and flat part facing to the wafer, and ameans for scanning said planar pad on said wafer, said manufacturingmethod comprises: a step for setting a wafer on said wafer stage, a stepin which a gas that is used for generating plasma is supplied into saidvessel by means of said gas supply means maintaining the internal ofsaid vessel at a reduced pressure by use of said vacuum pump to therebygenerate plasma in said vessel by means of said means for generatingplasma; a step for cleaning the main surface of said wafer by applyingthe viscous friction force exerted due to gas flow of a first gasinjected from said gas hole onto the main surface of said wafer that isbrought close to the flat part of said planar pad and by applying actionof electrons or radicals generated by said plasma together; a step inwhich plasma is generated using a second gas in said vessel after saidcleaning step and the main surface of said wafer is exposed to plasma;and a step for transferring said wafer to the outside of said vessel,wherein a step for cleaning the main surface of said wafer with actionof electric charges or radicals generated from plasma is added as apre-treatment after the step in which plasma is generated in saidvessel, and wherein a step for cleaning the main surface of said waferwith action of electric charges or radicals generated from plasma and astep for cleaning the main surface of said wafer with cooperative actionof viscous friction force due to gas flow of said first gas injectedfrom said gas hole of said planar pad having a flat part which is closeto the main surface of said wafer and with action of electric charges orradicals generated from plasma that are applied simultaneously.
 15. Amanufacturing method for semiconductor devices by use of a dry cleaningsystem having a vessel connected to a vacuum pump, a means forgenerating plasma, a gas supply means for supplying gas that is used forgenerating plasma, a wafer stage on which a wafer is to be set providedin said vessel, a planar pad provided with a gas hole for injecting gastoward the wafer and flat part facing to the wafer, and a means forscanning said planar pad on said wafer, said manufacturing methodcomprises: a step for setting a wafer on said wafer stage, a step inwhich a gas that is used for generating plasma is supplied into saidvessel by means of said gas supply means maintaining the internal ofsaid vessel at a reduced pressure by use of said vacuum pump to therebygenerate plasma in said vessel by means of said means for generatingplasma; a step for cleaning the main surface of said wafer by applyingthe viscous friction force exerted due to gas flow of a first gasinjected from said gas hole onto the main surface of said wafer that isbrought close to the flat part of said planar pad and by applying actionof electrons or radicals generated by said plasma together; a step inwhich plasma is generated using a second gas in said vessel after saidcleaning step and the main surface of said wafer is exposed to plasma;and a step for transferring said wafer to the outside of said vessel,wherein said dry cleaning system is provided with a wafer heating means,and said wafer is heated by means of said wafer heating means during astep for cleaning the main surface of said wafer and during a step forexposing the main surface of said wafer to plasma of the second gas. 16.The manufacturing method for semiconductor devices according to claim15, wherein said wafer heating means is a heat source heated by means ofa current provided in said wafer setting means.
 17. The manufacturingmethod for semiconductor devices according to claim 15, wherein saidwafer heating means is an infrared lamp.
 18. A manufacturing method forsemiconductor devices by use of a dry cleaning system having a vesselconnected to a vacuum pump, a means for generating plasma, a gas supplymeans for supplying gas that is used for generating plasma, a waferstage on which a wafer is to be set provided in said vessel, a planarpad provided with a gas hole for injecting gas toward the wafer and flatpart facing to the wafer, and a means for scanning said planar pad onsaid wafer, said manufacturing method comprises: a step for setting awafer on said wafer stage, a step in which a gas that is used forgenerating plasma is supplied into said vessel by means of said gassupply means maintaining the internal of said vessel at a reducedpressure by use of said vacuum pump to thereby generate plasma in saidvessel by means of said means for generating plasma; a step for cleaningthe main surface of said wafer by applying the viscous friction forceexerted due to gas flaw of a first gas injected from said gas hole ontothe main surface of said wafer that is brought close to the flat part ofsaid planar pad and by applying action of electrons or radicalsgenerated by said plasma together; a step in which plasma is generatedusing a second gas in said vessel after said cleaning step and the mainsurface of said wafer is exposed to plasma; and a step for transferringsaid wafer to the outside of said vessel, wherein said dry cleaningsystem is provided with a wafer heating means, and a step for heatingsaid wafer in said vessel for a certain time is added after saidcleaning step instead of said step for exposing the main surface of saidwafer to plasma generated from the second gas in said vessel.
 19. Amanufacturing method for semiconductor devices by use of a dry cleaningsystem having a vessel connected to a vacuum pump, a means forgenerating plasma, a gas supply means for supplying gas that is used forgenerating plasma, a wafer stage on which a wafer is to be set providedin said vessel, a planar pad provided with a gas hole for injecting gastoward the wafer and flat part facing to the wafer, and a means forscanning said planar pad on said wafer, said manufacturing methodcomprises: a step for setting a wafer on said wafer stage, a step inwhich a gas that is used for generating plasma is supplied into saidvessel by means of said gas supply means maintaining the internal ofsaid vessel at a reduced pressure by use of said vacuum pump to therebygenerate plasma in said vessel by means of said means for generatingplasma; a step for cleaning the main surface of said wafer by applyingthe viscous friction force exerted due to gas flow of a first gasinjected from said gas hole onto the main surface of said wafer that isbrought close to the flat part of said planar pad and by applying actionof electrons or radicals generated by said plasma together; a step inwhich plasma is generated using a second gas in said vessel after saidcleaning step and the main surface of said wafer is exposed to plasma;and a step for transferring said wafer to the outside of said vessel,wherein a film deposited by means of spattering is provided on the mainsurface of said wafer set on said wafer stage.